1. Field of the Invention
The invention relates to paperboard, corrugated or similar cartons and containers made from a one piece flat blank, having panels that are preliminarily folded and glued such that the container is manufactured in a knocked-down flat configuration, and is erected into a rectilinear box when loaded with product. According to the invention, the folded and glued panels of a one-piece erectable blank with self-erecting gusset corners, comprise container end walls with spaced inner and outer end wall panels and an upper ledge. The end wall panels and ledge encompass hollow erectable support columns associated with upwardly protruding stacking tabs. The stacking tabs are spaced inwardly from the container ends and serve to lock down opposite top or lid flaps after the container is loaded. The container is particularly apt for agricultural products and can be supplied in a stack of knocked-down container forms that are erected, loaded, closed and stacked with only a few quick movements.
At the corners of the container, self-erecting bellows or gusset joints are provided at which diagonally folded panels between the end and side walls are glued to an inner face of the outer end wall panels. When erected by folding the end wall panels upright relative to the bottom, the side walls and end walls pull one another into an upright rectilinear shape.
The end walls are vertically reinforced by the internal hollow columns, which are disposed under the ledge in the erected state of the container. Column-forming panels extend laterally from the inner end wall panel of the flat blank. These column-forming panels are preliminarily scored, folded laterally inwardly and are glued to the inner end wall panels exclusively at ends of the column-forming panels. The columns are opened at the folds and scores, from a flat parallelogram into a column with rectangular cross section, by lateral inward pressure. During erection of the container, the columns are manually pressed laterally inwardly as the end walls are folded longitudinally inwardly between the side walls. The erected side walls old the hollow columns open and the end walls wrap around the columns and lock into the bottom by tabs inserted into openings in the container bottom
At least one stacking tab is defined to protrude from the inner end wall panel to which the column forming panels are glued. The inner end wall panel and the column-forming panels have corresponding tabs that are glued together in two thicknesses. Thus a two-thickness tab protrudes upwardly from the surface of the erected container for engagement in an opening in the underside of an overlying container of the same type.
Inasmuch as the stacking tabs are integral with the inner end wall panels and the column-forming panels, the stacking tabs can be spaced longitudinally inwardly from the outer end walls of the container. The tabs are cut with a barbed shape and function as locking clasps to hold the opposite top panels closed, when folded inwardly from front and rear side walls.
The container can be cut from flat stock,scored and formed into a knocked-down-flat state entirely by automated means, namely a fold-and-glue machine that applies glue and folds the panels s the blank is fed through the machine. The container is erected on site by simply folding in the end walls. When loaded, the container is closed and locked by pushing down the top flaps, and is stackable in registry with very good vertical stacking support.
2. Prior Art
Corrugated and paperboard containers are made from pieces that are cut in required shapes from sheet stock, and are assembled to form the walls of a full or partial enclosure. Variations are possible in which several integral parts are formed and then assembled using glue, tape, staples or the like. For example, the container body and lid may be separate parts, or various types of inserts may be used for reinforcement or other purposes such as subdividing the volume of the container into discrete areas. Containers are supplied in a collapsed state because storage or handling of empty containers is wasteful of space. The containers are partly formed, with their parts cut out and certain seams and folds provided. The packer erects the containers prior to loading, finishing any required assembly steps in the process, and finally closes the loaded containers for storage or shipment. For example, a container may be cut out from integral flat stock, folded and scored for the corners of the container (with least one seam), and supplied with the opposite side and end walls collapsed flat against one another. Top and bottom flaps are likewise integrally attached to the side and end walls at folds or score lines. The packer erects the container from a flat parallelogram into its rectilinear shape, folding the top or bottom flaps inwardly before and after loading, and finally closing the container at seams that are taped, glued or otherwise attached.
It is efficient to provide a form of container in which all the container parts are Integral extensions of a single piece of flat material. Separate parts such as discrete lids, partitions and reinforcing inserts involve manual assembly steps. Manual assembly steps consume worker time and are costly. In addition, assembly steps can be physically taxing and may lead to repetitive motion injuries. It is preferable if containers are substantially fully formed when supplied, and require the least possible manual action to deploy, load, close and store or pack the containers for shipment.
Self-erecting paperboard and corrugated containers are known with their respective wall panels and flaps connected in such a way that one or more of the structural parts of the container is pulled into an erected position as the other parts are erected. Commonly owned pending patent application Ser. No. 09/129,375, filed Aug. 5, 1998 and entitled Stackable Container--Sheffer discloses an integral blank container having bellows or gusset corners that couple a bottom panel with side and end wall panels to pull the respective panels into a rectilinear shape when the container is erected from a knocked-down-flat configuration by folding end wall panels perpendicular to the bottom panel. U.S. Pat. No. 4,899,929--Grollman likewise discloses self-erecting bottom flaps connected to container side walls by folded-back glued panels arranged to pull the bottom flaps downwardly when the side walls are erected by expanding the container from a flattened parallelogram.
The foregoing Sheffer application also discloses a locking tab structure in which a plural thickness tab protrudes upwardly from the structure of the container end wall to engage in an opening in a similar container stacked thereon. One objective of cartons or containers as described is to bear the load of products loaded into the containers, as well as to bear the load of additional containers that may be stacked on a given container For this purpose, the panels that are folded and glued can include wall panels having multiple thicknesses of glued-together material and/or partition walls that extend between opposite side walls or end walls. These structural reinforcing features add to the vertical stacking strength or load bearing capacity of the container, namely the maximum vertical weight that can be borne without buckling or displacing the container walls. A container should have good vertical stacking strength, but if possible such stacking strength should be achieved without unnecessarily adding weight to the container. It is also advantageous if stacking strength can be achieved by means of reinforcements that occupy very little of the space that would otherwise be available for carrying product. Thus, considerations of container strength are sometimes at odds with considerations of weight and volume.
Containers are routinely stacked vertically to make efficient use of space, and may be reinforced against vertical crushing by employing multiple thickness of material for wall panels or by forming columns, for example as in U.S. Pat. No. 5,330,094--Merz. Known structures that are reinforced in this manner are constructed using separate inserts or using a container structure that requires various manual operations in order to install or erect the reinforcing structure
Two or more containers are stacked in vertical registry to be carried manually, to be stacked in a storage area or for shipping on a pallet or the like, in any number of adjacent columns or in a staggered overlapping arrangement resembling masonry. Stacking maximizes the density of storage, and often enables a group of containers to be handled conveniently as a unit using a fork truck or two wheel hand dolly.
Containers in stacks may be subjected to various vertical and lateral forces. Vertical compression force is applied by the weight of upper containers in a stack and the product they contain. This vertical force is borne by vertically extending structural elements in the underlying cartons. The structural elements that bear vertical forces on a carton or similar container normally occupy only a limited span of lateral width and/or depth. For example, the vertical forces on many cartons are borne exclusively by their vertical side and end walls If the stacked cartons remain in registry, then the weight of each upper container is coupled by the side and end walls of the upper container to corresponding side and end walls of an underlying container, because the side and/or end walls of the upper and lower containers are disposed directly over and under one another. When the containers are displaced from exact registry, vertical support may be lacking. It is possible to enlarge the lateral width and depth of the side or end walls of a container such that a ledge is defined on which an upper container will rest up to a certain amount of container misalignment in the stack. An example of a ledge structure is disclosed in the foregoing Sheffer application. Registry tabs are also provided in U.S. Pat. No. 5,839,650--Sheffer. However, it is difficult to arrange for a ledge in a manner that is consistent with the objectives of fold-and-glue cartons, for example, to provide a knocked-down flat pre-erection blank for shipping that can be erected with a minimum of manual actions, to conserve container volume of product, and to ensure adequate vertical stacking strength. It would be advantageous if these objectives could all be balanced to provide an optimal container.
The present invention, as in the Sheffer pending application, provides a site-erected container or carton that is entirely formed from an integral flat blank. The only assembly required is erection from a knocked-down-flat configuration by folding the end walls into position to lock into the bottom panel. In so doing, the end and side walls are simultaneously erected perpendicular to the bottom panel; the end walls are provided with registry tabs on a stacking ledge, and are reinforced by the internal columns. The container is supplied with substantially all its joints pre-attached and can be produced automatically using a fold-and-glue container production machine, for example as available from Bobst Group, Inc., 146 Harrison Avenue, Roseland, N.J. 07068 (affiliated with Bobst, S A, Lausanne, C H). At the loading site the user need only fold the end panels into place, fill the container and press down the top flaps to produce a stackable unit that is readily handled, stacked on a pallet or otherwise processed for storage or shipment.